remove extra byte data

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Sam Hackett

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May 15, 2018, 6:25:16 PM5/15/18

to LAStools - efficient tools for LiDAR processing

Hi,

I have LAS data that has come out of the back end of Height Above Ground calculations with the '-store_as_extra_bytes'. It appears the extra bytes are messing up importing the LAS into another program. Is there a command to remove the extra bytes?

Thanks

Sam

Martin Isenburg

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May 15, 2018, 6:48:39 PM5/15/18

to LAStools - efficient command line tools for LIDAR processing

Hello,

I guess I should add this functionality. For the time being you can do the trick shown below. You need to know the point size without extra bytes (type 0 = 20 bytes, type 1 = 28 bytes, type 2 = 26 bytes, type 3 = 34 bytes, ...0) and you need to know the index of the VLR describing the extra bytes in the LAS header.

Here the point size is 1 so I reset its size back down to 28. And here the VLR describing the extra bytes in the LAS header is the second one and it's index in the array of VLRs is 1.

:: adding extra bytes

lasheight -i ..\data\fusa.laz ^

-classify_above 7.5 8 ^

-store_as_extra_bytes ^

-o fusa_extra.laz

:: removing extra bytes and description

las2las -i fusa_extra.laz ^

-set_point_size 28 ^

-remove_vlr 1 ^

-o fusa_noextra.laz

:: relevant lasinfo reports

e:\LAStools\bin>lasinfo -i ..\data\fusa.laz

lasinfo (180429) report for '..\data\fusa.laz'

reporting all LAS header entries:

file signature: 'LASF'

file source ID: 0

global_encoding: 0

project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000

version major.minor: 1.1

system identifier: 'LAStools (c) by Martin Isenburg'

generating software: 'lasclassify (110920) unlicensed'

file creation day/year: 40/2010

header size: 227

offset to point data: 321

number var. length records: 1

point data format: 1

point data record length: 28

number of point records: 277573

number of points by return: 263413 13879 281 0 0

scale factor x y z: 0.01 0.01 0.01

offset x y z: 0 0 0

min x y z: 277750.00 6122250.00 42.21

max x y z: 277999.99 6122499.99 64.35

variable length header record 1 of 1:

reserved 43707

user ID 'LASF_Projection'

record ID 34735

length after header 40

description 'by LAStools of Martin Isenburg'

GeoKeyDirectoryTag version 1.1.0 number of keys 4

key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected

key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S

key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter

key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter

LASzip compression (version 2.0r1 c2 50000): POINT10 2 GPSTIME11 2

reporting minimum and maximum for all LAS point record entries ...

X 27775000 27799999

Y 612225000 612249999

Z 4221 6435

intensity 10 62293

return_number 1 3

number_of_returns 1 3

edge_of_flight_line 0 0

scan_direction_flag 0 0

classification 1 6

scan_angle_rank 79 103

user_data 0 197

point_source_ID 1 1

gps_time 5880.963028 5886.739738

number of first returns: 263413

number of intermediate returns: 283

number of last returns: 263370

number of single returns: 249493

overview over number of returns of given pulse: 249493 27232 848 0 0 0 0

histogram of classification of points:

17553 unclassified (1)

180868 ground (2)

37030 high vegetation (5)

42122 building (6)

=========================

e:\LAStools\bin>lasinfo -i fusa_extra.laz

lasinfo (180429) report for 'fusa_extra.laz'

reporting all LAS header entries:

file signature: 'LASF'

file source ID: 0

global_encoding: 0

project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000

version major.minor: 1.1

system identifier: 'LAStools (c) by rapidlasso GmbH'

generating software: 'lasheight (180429) commercial'

file creation day/year: 40/2010

header size: 227

offset to point data: 567

number var. length records: 2

point data format: 1

point data record length: 30

number of point records: 277573

number of points by return: 263413 13879 281 0 0

scale factor x y z: 0.01 0.01 0.01

offset x y z: 0 0 0

min x y z: 277750.00 6122250.00 42.21

max x y z: 277999.99 6122499.99 64.35

variable length header record 1 of 2:

reserved 43707

user ID 'LASF_Projection'

record ID 34735

length after header 40

description 'by LAStools of Martin Isenburg'

GeoKeyDirectoryTag version 1.1.0 number of keys 4

key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected

key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S

key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter

key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter

variable length header record 2 of 2:

reserved 0

user ID 'LASF_Spec'

record ID 4

length after header 192

description 'by LAStools of rapidlasso GmbH'

Extra Byte Descriptions

data type: 4 (short), name "height above ground", description: "vertical point to TIN distance", scale: 0.01, offset: 250

LASzip compression (version 3.2r3 c2 50000): POINT10 2 GPSTIME11 2 BYTE 2

reporting minimum and maximum for all LAS point record entries ...

X 27775000 27799999

Y 612225000 612249999

Z 4221 6435

intensity 10 62293

return_number 1 3

number_of_returns 1 3

edge_of_flight_line 0 0

scan_direction_flag 0 0

classification 1 8

scan_angle_rank 79 103

user_data 0 197

point_source_ID 1 1

gps_time 5880.963028 5886.739738

number of first returns: 263413

number of intermediate returns: 283

number of last returns: 263370

number of single returns: 249493

overview over number of returns of given pulse: 249493 27232 848 0 0 0 0

histogram of classification of points:

17131 unclassified (1)

180868 ground (2)

31803 high vegetation (5)

32255 building (6)

15516 keypoint (8)

=========================

e:\LAStools\bin>lasinfo -i fusa_noextra.laz

lasinfo (180429) report for 'fusa_noextra.laz'

reporting all LAS header entries:

file signature: 'LASF'

file source ID: 0

global_encoding: 0

project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000

version major.minor: 1.1

system identifier: 'LAStools (c) by rapidlasso GmbH'

generating software: 'las2las (version 180512)'

file creation day/year: 40/2010

header size: 227

offset to point data: 321

number var. length records: 1

point data format: 1

point data record length: 28

number of point records: 277573

number of points by return: 263413 13879 281 0 0

scale factor x y z: 0.01 0.01 0.01

offset x y z: 0 0 0

min x y z: 277750.00 6122250.00 42.21

max x y z: 277999.99 6122499.99 64.35

variable length header record 1 of 1:

reserved 43707

user ID 'LASF_Projection'

record ID 34735

length after header 40

description 'by LAStools of Martin Isenburg'

GeoKeyDirectoryTag version 1.1.0 number of keys 4

key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected

key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S

key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter

key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter

LASzip compression (version 3.2r3 c2 50000): POINT10 2 GPSTIME11 2

reporting minimum and maximum for all LAS point record entries ...

X 27775000 27799999

Y 612225000 612249999

Z 4221 6435

intensity 10 62293

return_number 1 3

number_of_returns 1 3

edge_of_flight_line 0 0

scan_direction_flag 0 0

classification 1 8

scan_angle_rank 79 103

user_data 0 197

point_source_ID 1 1

gps_time 5880.963028 5886.739738

number of first returns: 263413

number of intermediate returns: 283

number of last returns: 263370

number of single returns: 249493

overview over number of returns of given pulse: 249493 27232 848 0 0 0 0

histogram of classification of points:

17131 unclassified (1)

180868 ground (2)

31803 high vegetation (5)

32255 building (6)

15516 keypoint (8)

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Sam Hackett

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May 15, 2018, 7:43:06 PM5/15/18

to LAStools - efficient tools for LiDAR processing

Thanks Martin,

Empowered with that knowledge I'm sure I can sort that.

For my data;

point data format = 1

point data record length = 30 (so this will be reduced to 28)

VLR record is 2 of 2

so I will use;

-set_point_size 28 ^

-remove_vlr 2 ^

Thanks for the quick response... you're not on an aircraft bound for a tropical paradise for a change ;-)

lasinfo (180303) report for Class3.las


reporting all LAS header entries

:


  file signature:             'LASF'
  file source ID:             0


  global_encoding:            1


  project ID GUID data 1-4:   00000000-0000-0000-0000-000000000000


  version major.minor:        1.3


  system identifier:          'LAStools (c) by rapidlasso GmbH'


  generating software:        'las2las (version 180303)'
  file creation day/year:     236/2017
  header size:                235
  offset to point data:       575


  number var. length records: 2
  point data format:          1
  point data record length:   30


  number of point records:    2081788
  number of points by return: 1803175 185176 56434 23521 8824


  scale factor x y z:         0.01 0.01 0.01


  offset x y z:               400000 700000 0
  min x y z:                  409852.80 767980.32 5.21
  max x y z:                  413251.83 772343.40 87.11
  start of waveform data packet record: 0


variable length header record 1 of 2:


  reserved             0


  user ID              'LASF_Projection'
  record ID            34735
  length after header  40


  description          'by LAStools of rapidlasso GmbH'


    GeoKeyDirectoryTag version 1.1.0 number of keys 4
      key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected


      key 3072 tiff_tag_location 0 count 1 value_offset 2105 - ProjectedCSTypeGeoKey: NZGD2000 / Mount Eden 2000


      key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter
      key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter
variable length header record 2 of 2:
  reserved             0
  user ID              'LASF_Spec'
  record ID            4
  length after header  192
  description          'by LAStools of rapidlasso GmbH'
    Extra Byte Descriptions
      data type: 4 (short), name "height above ground", description: "vertical point to TIN distance", scale: 0.01, offset: 250


reporting minimum and maximum for all LAS point record entries ...


  X              985280    1325183
  Y             6798032    7234340
  Z                 521       8711
  intensity         418      65535
  return_number       1          7
  number_of_returns   1          7


  edge_of_flight_line 0          0
  scan_direction_flag 0          0


  classification      3          3
  scan_angle_rank   -29         16
  user_data           1          2
  point_source_ID  1107       1716
  gps_time 168586574.201361 170381688.662964
number of first returns:        1803175
number of intermediate returns: 520
number of last returns:         2080392
number of single returns:       1802299
WARNING: there are 3190 points with return number 6
WARNING: there are 1468 points with return number 7
overview over number of returns of given pulse: 1802299 185317 56755 23722 8943 3246 1506


histogram of classification of points:


         2081788  low vegetation (3)

Martin Isenburg

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May 15, 2018, 7:46:43 PM5/15/18

to LAStools - efficient command line tools for LIDAR processing

Hello,

Common miss-conception. The second VLR (2 of 2) has index 1 in the C/C++ style array of VLRs. Hence its '-remove_vlr 1' just like in my example.

Regards,

Martin

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